Method of treating p-6 alloys in the form of articles of substantial thickness including the step of warm working



United States Patent 3,410,733 METHOD OF TREATING P-6 ALLOYS IN THE FORM OF ARTICLES OF SUBSTANTIAL THICKNESS INCLUDING THE STEP 0F WARM WORKING Donald L. Martin, Elnora, N.Y., assignor to General Electric Company, a corporation of New York No Drawing. Filed Oct. -1, 1965, Ser. No. 492,314 4 Claims. (Cl. 148-120) This invention relates to a method of forming rods, tubes and other similar shapes by forging, swaging, rod drawing or rolling an alloy of 4347 percent cobalt, -7 percent nickel, 4-6 percent vanadium and the balance substantially all iron, as is described in US. Patent 2,596,705, and assigned to the same assignee as the present application. The alloy is commonly referred to as P-6 alloy.

White and Wahl Patent No. 1,862,559, granted June 14, 1932, outlines the difiiculty of working alloys very similar to the P-6 alloy. The material is hot worked into sheet material and any subsequent cold working is limited in extent.

The P-6 alloy may be cold rolled as a thin sheet. The cold reduction necessary to obtain the optimum magnetic properties is 75 percent of the area. While the 75 percent reduction on thin sheet material is readily obtained it is not easy to forge or swage the material with a 75 percent reduction when one produces an article such as rods or tubes that have a thickness of A to /2 inch. In certain cases after the forging or swaging of at least 75 percent is completed it may be desirable to finish machining the part Without heat treating. A heat treatment that would aid machining will destroy the advantageous magnetic properties. Likewise, it is not desirable to resort to the facing of the article with brass in order to prevent them from crumbling as outlined by White and Wahl patent, cited above. Attempts to swage an 0.83 inch diameter bar of P6 in the hot swaged condition at temperatures of 500 C. and 300 C. were unsuccessful. At 500 C. the bar cracked on the first pass. At 300 C. several passes were made before the cracking became severe and Without attaining a 75' percent reduction.

It is an object of the present invention to perfect a process which will permit the cold reduction of 75 percent in area of a 1P-6 alloy that is at least /1 inch in thickness prior to the cold reduction.

It is a further object of the present invention to perfect a process that will permit the cold forging, swaging, rod drawing or rolling or rods and tubing of the P-6 alloy.

It is a further object of the invention to produce a rod, tube or annular member of a P-6 alloy of optimum magnetic properties by cold working.

The P-6 alloy is austenitic at high temperatures and ferritic at room temperature. If cold working is applied to the alloy, any remaining austenitic is transformed to ferrite and the workability of the alloy decreased. It has been found that if the alloy is first heat treated at 1000" C. to 1200 C. for about one hour, quickly cooled, as by a Water quench, the alloy may be warm worked at temperatures of 200 to 600 C. in the range of 70-90' percent reduction. Further, the alloy may be forged or swaged without encountering the difiioulty outlined above as to cracking. [For example, an 0.83 inch bar was heat treated at 1050 C. for 1 hour, water quenched and swaged very well to 0.41 inch in diameter (representing a 75 percent reduction in area) at 300 C.

The DC. magnetic properties of the above example are as follows:

Condition H max B max. Br He As warm swaged 100 4, 000 2, 600 25 Aged 2 hrs. 625 C 100 11, 700 7, 000 50 D0 150 14, 800 10, 400 67 Aged 6 hrs. 625 C 150 I4, 560 10. 400 65 D0 200 16,000 11, 800 68 These magnetic properties are considered to be unusual for a piece with this mass.

In addition to the above treatments, in some cases it may be desirable to subject the article before or after the aging treatments at sub-zero temperatures to promote the transformation of the non-magnetic austenite to ferrite. One example of a temparture that is of practical significance is the boiling point temperature of liquid nitrogen, i.e., 196 C.

By virtue of this invention, the P-6 alloy can be used to build gyromotors since P-6 alloy laminations would not be subject to mass shift and the material in lamination form would not be subject to magnetostnictive effects when assembled under stress. For such use in hysteresis drive devices, the said alloy would be produced in rod or tube form, as described hereinabove, and cut in short lengths to provide the required laminae.

Having thus described this invention in such full, clear, concise and exact terms as to enable any person skilled in the art to which it pertains to rrrake and use the same, and having set forth the best mode contemplated of carrying out this invention, I state that the subject matter which I regard as being my invention is particularly pointed out and distinctly claimed in what is claimed, it being understood that equivalents or modifications of, or substitutions for, parts of the specifically described embodiments of the invention may be made without departing from the scope of the invention as set forth in what is claimed.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. The method of treating articles having a minimum thickness of at least /2 inch, of non-sheet form, and whose composition consists essentially of 4347% cobalt, 5-7% nickel, 4-6% vanadium and the balance iron, which compnises heat treating said articles at a temperature between about 1000 C. and about 1200" C. followed by quenching, warm working said articles at a temperature of 200-600 C. to produce a reduction in area in the range of 70 to and aging said articles.

2. The method of claim 1 wherein the aging is carried out at a temperature of 625 C.

3. The method of claim 1 wherein prior to the aging step said articles are treated at a sub-zero temperature of about 196 C.

4. The method of claim 1 wherein subsequent to the aging step said articles are treated at a sub-zero temperature of about -196 C.

References Cited.

UNITED STATES PATENTS 1,859,087 5/1932 Heinicke 148-120 1,862,559 6/1932 IWhite.

2,506,393 5/1950 Smoluchowski 148-120 2,596,705 5/ 1952 Martin.

2,801,942 8/1957 Nachman l48l2 XR 2,810,085 10/1957 Akeley 148-120 XR 3,144,363 8/1964 Aspden et a1 148-111 3,189,493 6/1965 Chen 148-121 XR 3,214,303 10/ 1965 Fiedler 148-111 3,279,960 10/1966 Nishihara et a1. 148-120 XR 3,301,720 1/1967 Griest 148-120 L. DEWAYNE RUTLEDGE, Primary Examiner. P. WE'I NSTEIN, Assistant Examiner. 

1. THE METHOD OF TREATING ARTICLES HAVING A MINUMUM THICKNESS OF AT LEAST 1/2 INCH, OF NON-SHEET FORM, AND WHOSE COMPOSITION CONSISTS ESSENTIALLY OF 43-47% COBALT, 5-7% NICKEL, 4-6% VANADIUM AND THE BALANCE IRON, WHICH COMPRISES HEAT TREATING SAID ARTICLES AT A TEMPERATURE BETWEEN ABOUT 1000*C. AND ABOUT 1200*C. FOLLOWED BY QUENCHING, WARM WORKING SAID ARTICLES AT A TEMPERATURE OF 200-600*C. TO PRODUCE A REDUCTION IN AREA IN THE RANGE OF 70 TO 90%, AND AGING SAID ARTICLES. 